[PATCH] rt2x00: Implement SW diversity

When mac80211 indicates that the default antenna setup
should be used _and_ that this default setup is SW_DIVERSITY.

This requires sampling and storing the RSSI per antenna
and check once every 2 seconds to determine if the RSSI
has changed significantly. Once this is the case we should sample
the other antenna for a short period and evaluate if
we need to swap antenna or not.

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 72 insertions, 15 deletions

diff --git a/drivers/net/wireless/rt2x00/rt2x00.h b/drivers/net/wireless/rt2x00/rt2x00.h
index d6f0a72b7a0c..e7533e2ccd2e 100644
--- a/drivers/net/wireless/rt2x00/rt2x00.h
+++ b/drivers/net/wireless/rt2x00/rt2x00.h
@@ -241,6 +241,43 @@ struct link_qual {
 };
 
 /*
+ * Antenna settings about the currently active link.
+ */
+struct link_ant {
+        /*
+         * Antenna flags
+         */
+        unsigned int flags;
+#define ANTENNA_RX_DIVERSITY    0x00000001
+#define ANTENNA_TX_DIVERSITY    0x00000002
+#define ANTENNA_MODE_SAMPLE     0x00000004
+
+        /*
+         * Currently active TX/RX antenna setup.
+         * When software diversity is used, this will indicate
+         * which antenna is actually used at this time.
+         */
+        struct antenna_setup active;
+
+        /*
+         * RSSI information for the different antenna's.
+         * These statistics are used to determine when
+         * to switch antenna when using software diversity.
+         *
+         *        rssi[0] -> Antenna A RSSI
+         *        rssi[1] -> Antenna B RSSI
+         */
+        int rssi_history[2];
+
+        /*
+         * Current RSSI average of the currently active antenna.
+         * Similar to the avg_rssi in the link_qual structure
+         * this value is updated by using the walking average.
+         */
+        int rssi_ant;
+};
+
+/*
  * To optimize the quality of the link we need to store
  * the quality of received frames and periodically
  * optimize the link.
@@ -259,11 +296,9 @@ struct link {
         struct link_qual qual;
 
         /*
-         * Currently active TX/RX antenna setup.
-         * When software diversity is used, this will indicate
-         * which antenna is actually used at this time.
+         * TX/RX antenna setup.
          */
-        struct antenna_setup active_ant;
+        struct link_ant ant;
 
         /*
          * Active VGC level
@@ -277,25 +312,47 @@ struct link {
 };
 
 /*
- * Update the rssi using the walking average approach.
+ * Small helper macro to work with moving/walking averages.
  */
-static inline void rt2x00_update_link_rssi(struct link *link, int rssi)
-{
-        if (link->qual.avg_rssi)
-                rssi = ((link->qual.avg_rssi * 7) + rssi) / 8;
-        link->qual.avg_rssi = rssi;
-}
+#define MOVING_AVERAGE(__avg, __val, __samples) \
+        ( (((__avg) * ((__samples) - 1)) + (__val)) / (__samples) )
+
+/*
+ * When we lack RSSI information return something less then -80 to
+ * tell the driver to tune the device to maximum sensitivity.
+ */
+#define DEFAULT_RSSI    ( -128 )
 
 /*
- * When the avg_rssi is unset or no frames  have been received),
- * we need to return the default value which needs to be less
- * than -80 so the device will select the maximum sensitivity.
+ * Link quality access functions.
  */
 static inline int rt2x00_get_link_rssi(struct link *link)
 {
         if (link->qual.avg_rssi && link->qual.rx_success)
                 return link->qual.avg_rssi;
-        return -128;
+        return DEFAULT_RSSI;
+}
+
+static inline int rt2x00_get_link_ant_rssi(struct link *link)
+{
+        if (link->ant.rssi_ant && link->qual.rx_success)
+                return link->ant.rssi_ant;
+        return DEFAULT_RSSI;
+}
+
+static inline int rt2x00_get_link_ant_rssi_history(struct link *link,
+                                                   enum antenna ant)
+{
+        if (link->ant.rssi_history[ant - ANTENNA_A])
+                return link->ant.rssi_history[ant - ANTENNA_A];
+        return DEFAULT_RSSI;
+}
+
+static inline int rt2x00_update_ant_rssi(struct link *link, int rssi)
+{
+        int old_rssi = link->ant.rssi_history[link->ant.active.rx - ANTENNA_A];
+        link->ant.rssi_history[link->ant.active.rx - ANTENNA_A] = rssi;
+        return old_rssi;
 }
 
 /*